Pneumatic ends out detection apparatus

ABSTRACT

PNEUMATIC APPARATUS FOR DETECTING THE LOSE OF RUNNING YARN ENDS DURING A TEXTILE MANUFACTURING OPERATION. SETECTION ON ENDS OUT IS ACCOMPLISHED BY GUIDING EACH YARN END OVER AN ORIFICE THROUGH WHICH PRESSURIZED GAS IS ESCAPING FROM A CONFINED AREA, THEREBY IMPEDING THE EXCAPE OF GAS AND ESTABLISHING A BACK PRESSURE IN THE CONFINED AREA. MEANS ARE PROVIDED FOR MONITORING SUCH BACK PRESSURE AND FOR PROVIDING A SIGNAL WHEN THE BACK   PRESSURE DROPS BELOW A PREDETERMINED LEVEL, SUCH DROP IN PRESSURE BEING OCCASIONED BY AN END OUT. ALSO DISCLOSED IS A SYSTEM IN WHICH THE PRESSURE IN THE SENSING HEADS REMAINS ESSENTIALLY CONSTANT AND ENDS OUT ARE DETECTED BY CHANGES IN AIR FLOW.

June 15, 1971 J. HARRIS 3,584,358

PNEUMATIC ENDS OUT DETECTION APPARATUS Filed Jan. 28, 1970 QEQQEQQEEEE ATTORNEYS United States Patent 3,584,358 PNEUMATIC ENDS OUT DETECTION APPARATUS James E. Harris, Bristol, Tenu., assignor to Eastman Kodak Company, Rochester, N.Y. Filed Jan. 28, 1970, Ser. No. 6,612 Int. Cl. D02h 13/02 US. Cl. 28-50 8 Claims ABSTRACT OF THE DISCLOSURE Pneumatic apparatus for detecting the loss of running yarn ends during a textile manufacturing operation. Detection of ends out is accomplished by guiding each yarn end over an orifice through which pressurized gas is escaping from a confined area, thereby impeding the escape of gas and establishing a back pressure in the confined area. Means are provided for monitoring such back pressure and for providing a signal when the back pressure drops below a predetermined level, such drop in pressure being occasioned by an end out. Also disclosed is a system in which the pressure in the sensing heads remains essentially constant and ends out are detected by changes in air flow.

The present invention relates to textile manufacturing and more particularly to improvements in ends out detection apparatus.

During many stages of textile manufacturing, it is common for a multitude of parallel yarn strands or end to be running at high speed from one position to another. When the loss of one or more ends occurs, as from a break or run out, it is desirable to immediately interrupt the manufacturing cycle and commence a rethreading operation in order to minimize the usual adverse effect on textile quality produced by such loss.

Heretofore a wide variety of ends out detectors have been devised for use in various textile manufacturing processes. One of the most popular varieties employs a fly wire as a means for sensing the presence or absence of yarn ends. In detectors of this type, the tension in the yarn ends is used to retain a movably mounted wire, usually operably connected with the on-off switch of a textile machine, in such a position as to permit the textile manufacturing operation to continue. In the event of a loose end, the unsupported wire drops into a second position wherein the machine is deactivated for rethreading purposes. Typical of such a detector is that disclosed by E. F. Saunders et al., in US. Pat. No. 2,734,334.

Although ends out detectors of the fly wire variety have proven successful in many textile operations, they are generally considered complex in construction, usually requiring delicate balancing of the moving components. Such construction has obvious adverse effects on cost considerations and reliability. Other disadvantages of fly wire detectors are: 1) they are inherently sensitive to normal variations in yarn tension and chatter, such as produced from winder traverse, and often produce false alarms and needless interruptions of the manufacturing cycle; (2) the ends have a tendency to snag on the wire sensors as they come into contact therewith; and (3) the wire sensors exert a drag on the yarn ends which may have a damaging effect thereon.

.Although photoelectric ends out detectors overcome many of the problems associated with the electromechanical fly wire detectors, such detectors are often limited in their application. For example, because of the possibility of arcing, photoelectric detectors are impractical for use in explosive environments, such as surround the manufacture of acetate yarn.

3,584,358 Patented June 15, 1971 Accordingly, it is the principal object of the present invention to provide improved ends out detection apparatus for use in textile manufacturing, such apparatus having none of the aforementioned disadvantages of prior art detectors. This objective is accomplished by the provision of an ends out detector which is capable of sensing the presence or absence of yarn ends pneumatically, rather than electromechanically or photoelectrically as in prior art devices. The apparatus includes a tubular yarn sensing head which is adapted to contain pressurized gas, preferably air, and has at least one aperture in the wall thereof through which the gas may escape into the atmosphere. Means such as yarn guides or grooves are provided for guiding a yarn end over the sensing head aperture as the yarn is advanced during the manufacturing process. The presence of the yarn end over the sensing head aperture tends to restrict the escape of pressurized gas from the head, thereby producing a back pressure in the sensing head and in the conduit providing the head with pressurized gas. Means are provided for sensing such back pressure and for interrupting the manufacturing process when the pressure drops below a predetermined level, as would be occasioned by an absence of a yarn end over the sensing head aperture; i.e. an ends out. Preferably, the sensing head is pressurized from a constant pressure source and a fluidic resistor is arranged in the conduit to provide a measurable pressure drop in the conduit when the loss of an end occurs. The fluidic resistor also serves the function of preventing the constant pressure source from restoring the pressure in the conduit to that value existing prior to the loss of ends, thereby permitting the interruption in textile operation to last until rethreading has been completed.

According to another embodiment of the invention, means are provided for determining the precise number of ends which are being advanced past the ends out detector at a particular time. Preferably, the apparatus includes one or more yarn sensing heads, each of which is capable of sensing the presence of a plurality of ends, and fluidic resistor which is arranged in the conduit providing the sensing heads with pressurized gas. A differential pressure gauge is employed to monitor the pressure across the fluidic resistor and means are provided for linearizing the relationship between the pressure drop across the fluidic resistor and the number of ends out.

Having described the improved ends out detector of the invention in general terms, reference is now made to the accompanying drawings wherein preferred embodiments are depicted and wherein:

FIG. 1 is an isometric view of the apparatus according to a preferred embodiment of the invention;

FIG. 2 is an enlarged side elevational view of the ends out sensing head depicted in FIG. 1.

FIG. 3 is a schematic diagram of ends out apparatus capable of indicating the number of loose ends at any given time.

Referring now to FIG. 1, pneumatic ends out detection apparatus in accordance with a preferred embodiment of the invention is depicted sensing the presence of yarn ends Y which are being advanced in the direction indicated by the arrows. Basically, the ends out apparatus comprises a tubular yarn sensing head 10 which is adapted to sense the presence or absence of two yarn strands; tubular conduit 12 through which pressurized air may be introduced into the yarn sensing head; a constant pressure air supply consisting of an air source S and a constant pressure regulator 14 whereby the pressure in conduit 12 may be maintained at a substantially constant level; a fluidic resistor 16 positioned in the conduit between the constant pressure regulator 14 and the yarn sensing head 10; and a diaphragm pressure switch 17 which is operably connected with the off-on switch of a textile machine and/or an alarm mechanism of some sort through a pair of wire leads 18 and is arranged to respond to a predetermined decrease in pressure in conduit 12 existing between the fluidic resistor and the sensing head. Preferably a pressure gauge 19 is used for providing a visual indication of the pressure exist-ing in the conduit at any particular time.

As best shown in FIG. 2, the yarn sensing head comprises a substantially tubular housing 20, one end of which is closed. Housing 20 has a hollow portion 21 for receiving pressurized gas and a pair of parallel grooves 22 formed in the surface thereof, each groove functioning as a guide for a yarn end. At the base of each groove is a small orifice 23 which communicates with the hollow portion 21 and permits pressurized air in the sensing head to escape into the atmosphere.

In operation, yarn ends Y are passed over the sensing head with a wrap angle of approximately 12 and are guided over the orifices 23 by the grooves formed in thesensing head. Preferably, the base of each groove is flat so as to permit each yarn end to band over the orifice over which it is guided, and thereby substantially impede the escape of pressurized air from the sensing head. By

impeding the escape of air, a measurable back pressure in conduit 12 may be produced in the region between the fluid resistor 16 and the sensing head. Upon sensing this back pressure, the differential pressure switch 17 will remain closed so as to permit continued operation of the textile machine. In the event of a run out or break in one of the yarn ends, the back pressure in conduit 12 will gradually decrease due to the unimpeded escape of air through one of the orifices. The rate of decrease in pressure in the conduit is, of course, dependent upon the diameter of the orifice. When the pressure in conduit 12 downstream of the fluid resistor drops below a predetermined triggering level, pressure switch 17 will open, thereby interrupting the machine operation. By selecting a pressure triggering level substantially lower than the normal pressure in conduit 12, the detector may be made insensitive to normal variations in yarn tension and chatter which might cause slight variations in back pressure. Due to the presence of the fluidic resistor 16, the pressure in the conduit resulting from an end out will remain below the switch triggering level until the rethreading operation has been completed and the yarn end is once again in place over the orifice. By selecting a pressure switch having a large diaphragm (e.g. four inches in diameter) relative to the size of the sensing head orifice, the pressure drop produced by an end out may be highly amplified, thereby providing for a very positive switching of the pressure switch.

Referring now to FIG. 3, apparatus for providing a visual indication of the number of yarn ends traveling along a predetermined path is shown schematically. The

apparatus depicted is designed to detect a maximum of 16 yarn ends. The apparatus comprises a pair of sensing heads 30, 30' each of which is designed similar to the sensing head depicted in FIG. 2, except that each head is provided with 8 yarn sensing orifices 31 and grooves 32 for guiding yarn ends over such orifices. The sensing heads are provided with air via conduit 35 from a source of constant pressure air S. A conventional constant pressure regulator 36 is positioned in the conduit for maintaining a substantially constant pressure therein. On the upstream side of regulator 36 is a flow sensing fluidic resistor 37 across which the pressure drop is monitored by a differential pressure gauge 38. A restricting orifice 39 serves to restrict the flow of air to the difierential pressure gauge and thereby reduce its sensitivity to rapid fluctuations in pressure which might be introduced by variations in yarn tension and chatter. The restricting orifice 40 and needle valve 42 are used as a bias adjustment to compensate for air loss through the yarn when no ends are missing thus allowing the gauge to be set to zero. Preferably, the gauge is provided with alarm set points whereby an alarm may 4 be sounded in response to the loss of a predetermined number of ends.

Theoretically, the rate at which air escapes from the sensing head and the consequential pressure drop across the fluidic resistor 37 is directly proportional to the number of yarn ends missing. However, because the pressure drop through the fluidic resistor may not be linear with air flow, and because some air leaks from the orifices even when they are covered by yarn ends, the relationship between the pressure drop across fluidic resistor 37 and the number of yarn ends missing is non-linear. For this reason a compensating fluidic resistor 41 is positioned in the conduit between the constant pressure regulator and the sensing heads. The compensating fluidic resistor serves to decrease the sensing head pressure slightly with each loss of a yarn end and in this manner produces a substantially linear relationship between the pressure drop across fluidic resistor 37 and end loss.

From the foregoing it is apparent that an ends out detector is provided which suifers none of the disadvantages of prior art devices. The ends out detector of the invention is inexpensive to manufacture, requiring no moving parts. It may be employed in explosive environments since there is no necessity for any portion of an electric circuit to be in close proximity to the running yarn ends. The flow of air against the yarn exerts little or no drag on the ends and there is substantially no chance for snagging. Due to the high amplification factor provided by the ratios of the diameters of the diaphragm in the differential pressure switch and the sensing head orifice, a very positive switching action may be obtained. Moreover the detector of the invention can be made insensitive to normal variations in yarn tension and chatter by adjustment of the pressure in the conduit or by varying the size of the constriction in the conduit provided by the fluidic resistor.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

I claim:

1. Ends out detection apparatus for providing a signal in response to the detection of a discontinuity in a strand of material travelling along a predetermined path, said apparatus comprising:

a source of fluid pressure;

means defining an aperture;

conduit means operably connecting said source with said aperture;

means defining a constriction in said conduit means upstream from said aperture;

means for guiding said strand across said aperture defining means, whereby the fiow of fluid through said aperture may be impeded by the presence of said material when travelling along said path, thereby producing a predetermined pressure drop across said restriction; and

means operably coupled with said conduit means for providing said signal in response to a predetermined change in said pressure drop across said constriction.

2. Ends out detection apparatus for providing a signal in response to the detection of a discontinuity in a yarn end being advanced along a predetermined path, said apparatus comprising:

a discontinuity sensing head comprising a housing having an arcuate outer surface portion, and means defining an opening through which pressurized fluid may be introduced;

a source of constant fluid pressure;

conduit means, operably coupled with said housing opening for introducing pressurized fluid into said housing;

means defining an orifice in said arcuate outer surface portion of said housing through which pressurized fluid in said housing may escape the confines of said housing;

means for guiding a yarn end across said orifice whereby the escape of fluid from said housing may be restricted; means defining a constriction in said conduit means whereby a substantial pressure drop in said conduit means many be effected in response to the removal of the yarn end from across said orifice;

signalling means, operably coupled with said conduit, and responsive to a predetermined change in said pressure drop across said constriction, whereby said signal may be provided in the event that pressurized fluid is permitted to flow through said aperture unimpeded by the presence of said yarn end.

3. The apparatus as set forth in claim 2, wherein said housing is substantially tubular in shape.

4. The apparatus as set forth in claim 2, wherein said tubular housing is provided with means defining a groove in the side wall thereof whereby said yarn end may be guided along said predetermined path, and said aperture defining means in said tubular housing is at the base of said grove.

5. The apparatus as set forth in claim 2, wherein the base of said groove is substantially flat as viewed tangential to said arcuate surface.

6. For use with a textile machine whereto or wherefrom a continuous strand of elongated textile material is to be advanced along a predetermined path, said machine including means whereby said machine may be deactivated, apparatus for senusing a discontinuity in said strand or a displacement of said strand from said predetermined path in excess of a predetermined amount and for deactivating said machine in response to the sensing of such discontinuity or path displacement, said apparatus comprising:

a source of fluid pressure;

a discontinuity and path displacement sensor comprising a member having open and closed ends, guiding means associated with the outer surface of said member, and means defining an aperture in the wall of said member through which a fluid may pass, whereby said strand may be guided by said guiding means to said textile machine along said predetermined path with the strand surface providing a resistance to fluid flow through said aperture defining means;

a flow conduit connecting said source with the open end of said member;

means defining a constriction in said conduit; and

means for monitoring the pressure in said conduit downstream from said constriction means, said monitoring means being operably coupled with said machine deactivating means, whereby said machine may be deactivated when the pressure in said conduit downstream from said constriction means drops below a 5 predetermined level, such drop being produced by the absence of said strand in front of said aperture.

7. Apparatus for providing a visible indication of the number of parallel yarn ends travelling along a predetermined path, said apparatus comprising:

a source of constant fluid pressure;

a housing adapted to receive pressurized fluid from said source, said housing having means defining a plurality of apertures in a wall thereof through which pressurized fluid in said housing may flow, the number of apertures being at least equal to the number of yarn ends;

conduit means for introducing pressurized fluid into said housing from said source;

means for guiding each of said yarn ends into close proximity with one of said apertures whereby the flow of pressurized fluid through said apertures may be impeded and a back pressure in said condiut produced;

means defining a first constriction in said conduit means upstream from said housing;

a differential pressure gauge operably coupled with said conduit across said constriction, whereby a visible indication of the pressure drop across said constriction References Cited 40 UNITED STATES PATENTS 2,438,365 3/1948 Hepp et al 28-51X 2,563,906 8/1951 AStill a a1. 66l63 4 LOUIS K. RIMRODT, Primary Examiner US. Cl. X.R. 

